Surgical headlights present a number of design problems which are not normally present in the design and construction of headlights used for other purposes (e.g. underground mining). For example, surgical headlights must be useable in the presence of volatile and often flammable or explosive materials such as alcohol and anesthesia gases. Further, such headlights should be designed and constructed to permit easy cleaning and sterilization.
With the advent of fiber optics, a number of improvements in surgical headlights have been made possible. For example, U.S. Pat. No. 3,645,254 described a surgical headlight in which fiber optics are used to transmit light rays from the light source to the light projecting element. The surgical headlight described in that patent includes a frictionally engaged ball joint carried by and at the rear of the light projecting element. This ball joint is held by a pair of opposed support arms carried by and at the front of a suitable headband. In a preferred form, the fiber optic cable passes through an aperture in the ball joint that is coaxial with the light projecting element. The surgical headlight shown in U.S. Pat. No. 3,645,254 is, in a sense, "universal" in that the wearer can freely adjust the direction of the light projecting element by simple movement of the light projector.
A different style of surgical headlight is shown in U.S. Pat. No. 3,745,993. The surgical headlight shown in that patent is supported from a headband by a pair of metal, spaced-apart vertical arms which are attached to the light projecting element by screws. These two screws act as pivot points on which the light projecting element may swivel in a vertical direction or arc, only. Thus, the surgical headlight shown in U.S. Pat. No. 3,745,993 is not "universal" in the sense of U.S. Pat. No. 3,645,254. Rather, the surgical headlight of U.S. Pat. No. 3,745,993 is intended to be "coaxial" with the visual axes of the wearer's eyes.
Although both of the surgical headlights shown in U.S. Pat. No. 3,645,254 and U.S. Pat. No. 3,745,993 have been manufactured and sold in the U.S.A. and are in widespread use, each of these two types of surgical headlights has certain disadvantages. For example, the light projecting element in the surgical headlight system shown in U.S. Pat. No. 3,645,254 protrudes a substantial distance from the wearer's forehead during use. If several surgeons are working on the same patient, their respective headlights sometimes interfere with each other. Further, the form of the headlight shown in the drawings of U.S. Pat. No. 3,645,254 is not "coaxial" with the visual axes of the wearer's eyes. In a somewhat similar fashion, the surgical headlight system of U.S. Pat. No. 3,745,993 is not a "universal" surgical headlight but rather it is free to move only in a vertical arc. This is a problem if the headband is not perfectly centered before use or if it is moved on the wearer's head during use. Further, neither of the surgical headlight systems shown in these two patents includes any means for adjusting the distance between its respective light projecting element and the support arms. Such adjustments are essential if the headlight is to be truly "coaxial" for wearer's of different facial configurations (e.g. high foreheads, low foreheads, etc.).